This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/EP01/02755 which has an International filing date of Mar. 12, 2001, which designated the United States of America and which claims priority on European Patent Application number EP 00106245.4 filed Mar. 22, 2000, the entire contents of which are hereby incorporated herein by reference.
The invention generally relates to a blade/vane. In particular, it relates to a turbine blade/vane, having at least one duct which is bounded by walls, a cooling fluid being admitted to an insert which is introduced into at least one duct.
A blade/vane is known from U.S. Pat. No. 5,419,039. Chambers, which extend in the direction of a longitudinal center line of the blade/vane, are formed between the insert and the walls of the blade/vane. The cooling fluid emerges from the insert into these chambers and impinges on the walls of the blade/vane. The cooling fluid subsequently flows along the walls and emerges through outlet openings into specially shaped chambers on the outside of the walls and from there into the surroundings. In the known blade/vane, the effect of the convection cooling, when the cooling fluid is flowing along the walls, is only slight because the flow length is greatly limited. In addition, mixing of the cooling fluid in the chambers occurs along the longitudinal center line of the blade/vane, so that no targeted cooling is possible.
Another blade/vane is known from WO 98/25009, which originates from the same assignee. This publication describes a blade/vane with walls which have a locally hollow configuration and through which a cooling fluid flows. A high level of cooling efficiency is achieved because of the reduction of the wall thickness in the region of the hollow chambers. Blades/vanes with such hollow walls, however, require a complicated casting procedure with high scrap rates and they are therefore very expensive.
An object of an embodiment of the present invention is, therefore, to make available a blade/vane which, using a simple manufacturing process, achieves an improvement in the cooling effect. According to an embodiment of the invention, an object may be achieved, in the case of a blade/vane, by at least one of the walls being provided with a number of horizontal ribs. These ribs may be arranged between the insert and the wall. Further, the insert may be provided with openings, through which the cooling fluid from the insert can enter between the horizontal ribs.
The horizontal ribs conduct the coolant along the wall of the blade/vane and prevent a flow of the coolant in the direction of the longitudinal center line of the blade/vane. Good convection cooling of the wall is, therefore, achieved. In addition, the horizontal ribs reinforce the blade/vane so that the wall thickness can be reduced. A reduction in the wall thickness leads to an increased cooling efficiency. The manufacture of the blade/vane can take place without complex cross section, using known methods. Hollow walls are not necessary. The scrap quota is therefore substantially reduced.
In an advantageous embodiment, the insert touches the horizontal ribs. The insert is supported and aligned in the desired position.
According to an advantageous development of one embodiment, the horizontal ribs, the insert and the wall may form chambers through which the cooling fluid flows. A flow of the cooling fluid in the direction of the longitudinal center line of the blade/vane may be reliably prevented by the chambers. In addition, the cooling effect can be varied, in a targeted manner, along the longitudinal center line of the blade/vane by differentially admitting cooling fluid to the chambers.
In an advantageous embodiment, the openings of the insert are arranged at a first end of the chambers and outlet openings for the cooling fluid are arranged in the wall at a second end of the chambers. The cooling fluid therefore flows along the wall to be cooled over the complete length of the chamber, so that the convection cooling is further improved.
The horizontal ribs can be arranged substantially at right angles to the longitudinal center line of the blade/vane. As an alternative, an angular position can be provided. In the case of an arrangement at right angles with respect to the longitudinal center line, the length of the horizontal ribs, and therefore of the chambers, is minimized. The angular position permits an increase in the length of the chambers and, therefore, further improved convection cooling.
The insert is advantageously closed at one end. In this case, the cooling fluid is only supplied from the other end of the insert. Emergence of the cooling fluid through the end facing away from the supply end is prevented, so that the cooling efficiency is increased. As an alternative, the cooling fluid can be supplied from both ends.
According to an advantageous embodiment, turbulators are used to reinforce the wall and merge into one another and into the horizontal ribs. By this, a substantial increase in the stiffness is achieved without additional material. For the same strength of the blade/vane, the wall thickness can be further reduced. Good heat exchange between the walls and the cooling fluid is achieved at the same time. The result is, therefore, a high cooling efficiency and a high overall efficiency.
The reinforcement of the wall does not only occur in the region of an individual turbulator. A large-area reinforcement is, in fact, provided by the connection of the turbulators to one another. The turbulators have, advantageously, a straight configuration. The use of straight turbulators permits a high level of reinforcement, in conjunction with simple manufacture.
According to an advantageous embodiment, the turbulators are arranged in such a way that, together with the horizontal ribs, they form recesses adjacent to one another in the form of polygons, in particular triangles or rhombuses. The inside of the wall is provided with a honeycomb structure. The individual polygons or honeycombs respectively form a closed cross section with high load-bearing capability and mutually support one another. A substantial increase in the stiffness can be achieved.
In an advantageous development, the wall thickness of the wall is reduced, at least in the region between the turbulators. This reduction in the wall thickness is made possible because the turbulators effect a reinforcement of the wall. Due to the reduction in the wall thickness, the cooling efficiency is further increased. In this arrangement, the turbulators can be advantageously used as metal feed ducts during the casting of the blade/vane. The honeycomb structure can therefore be conveniently manufactured.
The blade/vane according to an embodiment of the invention can be configured as guide vanes or as rotor blades of a turbomachine.